Detector for x-ray computer tomography scanners

ABSTRACT

A detector for x-ray computer tomography scanners, includes a number of adjacent detector lines extending in an x direction, whereby each detector line is formed from a multitude of adjacent scintillator elements. In order to increase the resolution in the z direction and to simplify the design of the detector, the surface of the scintillator elements are partially covered, which further serves to reduce the size of the aperture in the z direction.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE03/00739 which has an Internationalfiling date of Mar. 7, 2003, which designated the United States ofAmerica and which claims priority on German Patent Application number DE102 11 948.1 filed Mar. 18, 2002, the entire contents of which arehereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to an x-ray computer tomography scannercomprising a detector.

BACKGROUND OF THE INVENTION

A computer tomography scanner that includes a detector is known, forexample, from DE 195 02 574 A1. The detector of the known x-ray computertomography scanner is a so-called multi-line detector. It includes aplurality of detector lines that are arranged in the direction of theaxis of an object that is to be irradiated, for example, a patient. Theaforementioned axis is also referred to as the z axis. In an x directionrunning perpendicular to the z axis, each detector line consists of aplurality of adjacent scintillator elements.

In the z direction, the resolution of such a multi-line detector is afunction of the height of the scintillator elements in the z direction.For technical reasons, the height of the scintillator elements cannot bereduced at will. For this reason the resolution of conventionalmulti-line detectors in the z direction is limited.

SUMMARY OF THE INVENTION

An object of an embodiment of the invention is to reduce or eveneliminate at least one of the disadvantages according to the prior art.In particular, one aim, in one embodiment, is to disclose an x-raycomputer tomography scanner including a detector that is as simple aspossible and inexpensive to produce, with which an increased resolutionis possible in the z direction where there is a set number or height oflines.

According to an embodiment of the invention, a device that partiallycovers the surface of the scintillator elements is provided, whichpartially covers the surface of the scintillator elements, for reducingthe size of the aperture in the z direction. The step that is suggestedallows an increase in the resolution in the z direction, in a simple andinexpensive manner. The proposed solution is universal. Conventionalscintillator elements can be used. Retroactive conversion ofconventional multi-line detectors is also possible.

Usefully, the device for reducing the size of the aperture is formedfrom a plurality of parallel adjacent strips, the strips advantageouslycovering the edges of the scintillator elements that run in the xdirection. The proposed features also make it possible to usescintillator elements, the edges whereof have smaller openings in the xdirection.

According to a further embodiment, the strips are arranged apredetermined distance Δz apart in the z direction, such that thescintillator elements essentially have the same aperture in the zdirection. This makes the manufacture of the detector simpler.Furthermore, the device for reducing the size of the aperture caninclude transverse strips which cover the edges of the scintillatorelements that run in the z direction. Thus the aperture can be reducedin size in the x direction, too. In this case, the edges of thescintillator elements that extend in the z direction no longer have tobe of the quality required by the prior art.

The device for reducing the size of the aperture is advantageouslyformed in one piece in the manner of a surround that is attachable tothe detector surface that is formed by the scintillator surfaces. Thismakes the retroactive conversion of conventional multi-line detectorspossible. The surround is designed to be symmetrical with respect to aplane of symmetry that runs perpendicular to the z direction.

According to an advantageous embodiment, the device for reducing thesize of the aperture is manufactured from a metal that absorbs X-rayseffectively, preferably of lead or tungsten.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention will becomeevident from the description of illustrated exemplary embodiments givenhereinbelow and the accompanying drawings, which are given by way ofillustration only and thus are not limitative of the present invention,wherein:

FIG. 1 A detector arrangement according to the prior art, seen inperspective,

FIG. 2 a top view of a detector,

FIG. 3 the detector according to FIG. 2 with a surround according to anembodiment of the invention and

FIG. 4 the detector according to FIG. 3 with a further surroundaccording to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a focal point 1 of an x-ray beam emitter from which comes afan-shaped beam of x-rays blended together by a surround that is notshown, which beam penetrates an object 3 and impinges on a detector 4.The detector 4 has a plurality of parallel detector lines 5, each ofwhich is formed from a plurality of adjacent scintillator elements 6. Az axis that runs parallel to the axis of the irradiated object 3 ismarked with the reference character 7. The z axis is parallel to theaxis of rotation of a measuring system that includes the detector 4.

The measuring system rotates around the axis of rotation 7 such that theobject 3 is x-rayed at various angles of projection. From the detectorsignals produced during the above process, a computer 8 calculates animage of the object 3 which is reproduced on a monitor 9.

FIG. 2 shows a top view of the detector 4. The detector includes aplurality of adjacent detector lines 5 in the z direction. Each lineconsists of adjacent scintillator elements 6 in an x direction that runsperpendicular to the z direction. The scintillator elements 6 each havethe same height Δz and a uniform width Δh. The aperture of each of thedetector elements 6 is provided by the surface, which has the height Δzin the z direction and the width Δh in the x direction.

In FIG. 3 the detector surface created by all the surfaces of thedetector elements 6 is partially covered by a surround 10. The surround10 consists of strips 11 that run in the x direction, which are securedon both sides by edge strips 12 that run in the z direction. Thesurround 10 is usefully manufactured from lead or tungsten. The strips10 are arranged such that the edges of the detector elements 6 that runin the x direction are covered thereby. By way of the surround 10, theaperture of the detector elements 6 can be reduced in size in the zdirection in a simple manner. Fitting the surround 10 to the detectorsurface results in a smaller aperture Δz* in the z direction. Theproposed surround 10 allows the resolution in the z direction to beimproved in a simple manner.

In the embodiment shown in FIG. 4, the surround 10 that is shown in FIG.3 has additional transverse strips 13. The transverse strips 13 arefitted in such a way that the edges of the detector elements 6 arecovered thereby in the z direction. The transverse strips 13 and thestrips 11 form a grid. The aperture formed by the grid is rectangular indesign. The proposed further surround 10 is particularly advantageousbecause, where the scintillator elements are of a given size, theresolution can be improved thereby in a particularly simple manner, bothin the x and in the z direction. Conventional detectors can be providedwith such a surround without any great expense.

Exemplary embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

1. A detector for an X-ray computer tomography scanner, rotatable aroundan axis of rotation that runs parallel to a first direction, thedetector comprising: a plurality of adjacent detector lines extending ina second direction, wherein each detector line is formed from aplurality of adjacent scintillator elements and wherein an aperture ofeach of said scintillator elements for impinging X-rays is provided by asurface that has a length extending in the first direction and a widthextending in the second direction; and means, which partially covers thesurface of the scintillator elements, for reducing the size of theaperture in the first direction, said means for reducing the size of theaperture including a plurality of parallel adjacent strips.
 2. Detectoraccording to claim 1, wherein the strips cover the edges of thescintillator elements that run in the second direction.
 3. Detectoraccording to claim 2, wherein the strips are arranged in the firstdirection a predetermined distance apart, such that the scintillatorelements essentially have the same aperture in the first direction. 4.Detector according to claim 2, wherein the means for reducing the sizeof the aperture further includes transverse strips, which cover theedges of the scintillator elements that run in the first direction. 5.Detector according to claim 1, wherein the strips are arranged in thefirst direction a predetermined distance apart, such that thescintillator elements essentially have the same aperture in the firstdirection.
 6. Detector according to claim 5, wherein the means forreducing the size of the aperture further includes transverse strips,which cover the edges of the scintillator elements that run in the firstdirection.
 7. Detector according to claim 1, wherein the means forreducing the size of the aperture further includes transverse strips,which cover the edges of the scintillator elements that run in the firstdirection.
 8. Detector according to claim 1, wherein the means forreducing the size of the aperture is formed in one piece in the mannerof a surround that is attachable to the detector surface that is formedby the scintillator surfaces.
 9. Detector according to claim 1, whereinthe means for reducing the size of the aperture is manufactured from ametal that absorbs X-rays effectively.
 10. Detector according to claim1, wherein the means for reducing the size of the aperture ismanufactured from at least one of lead and tungsten.
 11. An X-raycomputer tomography scanner, comprising the detector of claim
 1. 12. AnX-ray computer tomography scanner, comprising: a detector, rotatablearound an axis of rotation that runs parallel to a first direction, thedetector including, a plurality of adjacent detector lines extending ina second direction, wherein each detector line is formed from aplurality of adjacent scintillator elements and wherein an aperture ofeach of said scintillator elements for impinging X-rays is provided by asurface that has a length extending in the first direction and a widthextending in the second direction; and a plurality of parallel adjacentstrips, which partially cover the surface of the scintillator elements,adapted to reduce the size of the aperture in the first direction. 13.The scanner of claim 12, wherein the strips cover the edges of thescintillator elements that run m the second direction.
 14. The scannerof claim 12, wherein the strips are arranged in the first direction apredetermined distance apart, such that the scintillator elementsessentially have the same aperture in the first direction.
 15. Thescanner of claim 12, wherein the detector further includes transversestrips, which cover the edges of the scintillator elements that run inthe first direction.
 16. The scanner of claim 12, wherein the pluralityof parallel adjacent strips are formed in one piece in the manner of asurround that is attachable to the detector surface that is formed bythe scintillator surfaces.
 17. The scanner of claim 12, wherein theplurality of parallel adjacent strips is manufactured from a metal thatabsorbs X-rays effectively.
 18. The scanner of claim 12, the pluralityof parallel adjacent strips are manufactured from at least one of leadand tungsten.
 19. A detector, rotatable around an axis of rotation thatruns parallel to a first direction, the detector comprising: a pluralityof adjacent detector lines extending in a second direction, wherein eachdetector line is formed from a plurality of adjacent scintillatorelements and wherein an aperture of each of said scintillator elementsfor impinging X-rays is provided by a surface that has a lengthextending in the first direction and a width extending in the seconddirection; and a plurality of parallel adjacent strips, which partiallycover the surface of the scintillator elements, adapted to reduce thesize of the aperture in the first direction.